In a Liquid Crystal Display (LCD) or an Organic Light Emitting Diode (OLED) display, each of a plurality of sub-pixel units is driven by a corresponding Thin Film Transistor (TFT), so that pictures may be displayed by the display at high speed, high brightness and high contrast.
The TFT functions as a switch for connecting a data line and a corresponding sub-pixel unit of the plurality of sub-pixel units. The TFT includes a gate, a source electrode and a drain electrode which is connected to the data line. Under the control of the gate, the data line charges or discharges a storage capacitor corresponding to the sub-pixel unit. If the TFT is in an on state, the drain electrode and the source electrode are connected, and an on-state current passes through a channel formed by a portion of an active layer between the source electrode and the drain electrode to charge the storage capacitor corresponding to the sub-pixel unit. If the TFT is in an off state, the drain electrode and the source electrode are disconnected, and the charging of the storage capacitor is stopped.